1. Field of the Invention
The present invention relates to a watercraft having a plurality of watercraft propulsion units, a generator disposed in each of the watercraft propulsion units, and a rudder deflecting system disposed in each of the watercraft propulsion units. The watercraft propulsion units are turned by the rudder deflecting systems thereby steering the watercraft.
2. Description of the Related Art
Conventionally, there are watercrafts of the kind described above, as shown in FIGS. 10, 11A, and 11B. The watercraft has a plurality of, herein two, outboard motors 1 as watercraft propulsion units. A generator 2 and a main battery 3 are connected to each of the outboard motors 1. The outboard motors 1 are steered by rudder deflecting systems 4.
That is, when an operator of the watercraft rotates a steering wheel (not shown), a rotational angle of the steering wheel is detected, and the signal is sent to the rudder deflecting system 4 of the outboard motor 1. An electric motor of the rudder deflecting system 4 is driven with electric power from the generator 2, the main battery 3, and the like, and the outboard motor 1 is steered.
On the other hand, when electric power from the main battery 3 is supplied to a starter motor of an engine of each of the outboard motors 1 and the engine is started, the generator 2 generates electric power from the drive of the engine. The main battery 3 is charged, and electric power is supplied to the rudder deflecting system 4.
The generator 2 also supplies electric power to a PTT (power trim and tilt system), an auxiliary device, and the like.
Further, a sub-battery (accessory battery) 5 is connected to the two generators 2. The sub-battery 5 supplies electric power to accessory devices such as an engine speed sensor, fishfinder, GPS, etc. (not shown). JP-A-2001-128388 discloses a watercraft of this kind.
However, in this kind of conventional watercraft, the generator 2 generates electric power for each of the outboard motors 1, and this electric power is supplied only to the rudder deflecting system 4 and the like of the individual outboard motor 1.
That is, a steering force acts on the outboard motor 1 because of a propeller reaction force, and thus the outboard motor 1 constantly requires steering. A steering load to one of the outboard motors 1 (for example, the outboard motor 1 on the starboard side) is larger than a steering load to the other outboard motor 1 (for example, the outboard motor 1 on the port side) in the case that the watercraft having a plurality of outboard motors 1 is turning, for example.
As a result, as shown in FIG. 11A, the main battery 3 of the outboard motor 1 on the port side is charged since consumption of electric power is smaller than an amount of generated electric power on that side. However, the main battery 3 of the outboard motor on the starboard side discharges electric power since consumption of electric power is larger than an amount of generated electric power on that side.
Therefore, the main battery 3 of the starboard side outboard motor 1 tends to be insufficiently charged, which causes the rudder deflecting system 4 to have an insufficient output.
To cope with this circumstance, the generator 2 may be arranged to supply the maximum electric power required by the outboard motor 1. However, this results in increases in both the size of the generator 2 and the cost.